Generator for driving a predefined load

ABSTRACT

Embodiments of the present invention are directed to a generator for connecting to a predefined load, where the generator is designed and constructed to meet one or more requirements of the predefined load. In specific embodiments the one or more requirements include providing a minimum output voltage while starting the predefined load at or above ambient temperature and providing an output voltage that does not exceed an upper voltage limit while being driven at full speed without any load current at or below ambient temperatures, while maintaining high efficiency under a specified full load running condition and keeping the overall cost and size of the generator low.

FIELD OF THE INVENTION

The present invention relates to a generator for connecting to apredefined load, where the predefined load has at least one or morevoltage requirements.

BACKGROUND

Generators convert motive power into electrical power for servingdifferent types of loads. Characteristics of loads and types of loads tobe served by the generators define the size, configuration, complexity,and cost of the generators. Although a lot of generators exist,different types of loads need new generators that meet specificrequirements of loads (e.g., voltage requirements, power requirements,size requirements, or the like). Thus, there exists a need for agenerator that meets specific requirements of a predefined loaddescribed herein.

SUMMARY

The following presents a simplified summary of one or more embodimentsof the invention in order to provide a basic understanding of suchembodiments. This summary is not an extensive overview of allcontemplated embodiments and is intended to neither identify key orcritical elements of all embodiments, nor delineate the scope of any orall embodiments. Its sole purpose is to present some concepts of one ormore embodiments in a simplified form as a prelude to the more detaileddescription that is presented later.

A generator for connecting to a load defines first embodiments of theinvention. The generator includes (i) a stator comprising at least aplurality of stator coils and a stator core with a plurality of statorslots, wherein the stator core comprises a stator lamination stack madeof steel, and (ii) a rotor comprising a rotor core with a rotorlamination stack made of the steel and a plurality of permanent magnetsfor establishing a rotating magnetic field within the generator. Thegenerator is structured to: (i) meet a hot generator, high current,transient loaded minimum voltage working point requirement bymaintaining relative apparent permeability of the steel below a firstlimit, and (ii) meet a cold generator, no load current working point,maximum voltage limit requirement.

In specific embodiments the generator is structured to meet the coldgenerator, no load current working point, maximum voltage limitrequirement by maintaining the relative apparent permeability above asecond limit.

In other specific embodiments of the generator, the first limit is 500and the second limit is 10.

In further specific embodiments of the generator, the output voltage ofthe generator is dependent on, at least in part, the relative apparentpermeability of the steel. In such embodiments, the relative apparentpermeability of the steel at the hot generator, high current, transientloaded minimum voltage working point requirement and the cold generator,no load current working point, maximum voltage point limit requirementis dependent on one or more of (i) a grade type of the steel (ii)magnetic polarization of the plurality of magnets, (iii) temperature ofthe generator, (iv) current drawn by the load, (v) size of thegenerator, (vi) number of series turns per phase of the generator, and(vi) inductance of the generator.

In one specific embodiment of the generator, the plurality of statorslots is 36 and the plurality of permanent magnets are 4. In anotherspecific embodiment of the generator, an outside diameter of the statoris between 253 mm and 342 mm. In another specific embodiment of thegenerator, a length of the stator lamination stack of the stator isbetween 145 mm and 196 mm.

In further specific embodiments of the generator, the generator isconnected to an induction motor load that drives a refrigeration unit tomaintain a temperature at or below 6 degree Celsius.

In further embodiments the present invention is directed to a generatorfor connecting to a predefined load. The generator includes a generatormagnetic circuit including at least in part a steel that is preselected.The generator is structured to (i) meet a hot generator, high current,transient loaded, minimum voltage point requirement by maintainingrelative apparent permeability of the steel below a first limit, and(ii) meet a cold generator, no load current, working point maximumvoltage limit requirement. In an embodiment, the first limit is 500. Ina related embodiment, the generator is structured to meet the coldgenerator, no load current, working point maximum voltage limitrequirement by maintaining the relative apparent permeability above asecond limit. In an embodiment, the second limit is 10.

In related embodiments, the generator magnetic circuit further includesa stator having at least a plurality of stator coils and a stator corewith a plurality of stator slots, wherein the stator core comprises astator lamination stack made of steel. In a specific embodiment of thegenerator, the outside diameter of the stator is between 253 mm and 342mm. In other specific embodiments of the generator, the length of statorlamination stack is between 145 mm and 196 mm and/or the plurality ofstator slots is 36.

In still further embodiments, the generator magnetic circuit furtherincludes a rotor including a rotor core with a rotor lamination stackmade of steel and a plurality of permanent magnets for establishing arotating magnetic field within the generator, in which, the core of therotor is made of the steel. In a specific embodiment of the generator,the plurality of permanent magnets is 4.

In further specific embodiments of the generator, the output voltage ofthe generator is dependent on, at least in part, the relative apparentpermeability of the steel. In such embodiments, the relative apparentpermeability of the steel is dependent on one or more of (i) a gradetype of the steel (ii) magnetic polarization of the plurality ofmagnets, (iii) temperature of the generator, and (iv) current drawn bythe load, (v) size of the generator, (vi) number of series turns of thegenerator and (vi) inductance of the generator.

A permanent magnet generator for a preselected load defines otherembodiments of the invention. The permanent magnet generator includes agenerator magnetic circuit. The generator magnetic circuit comprises, atleast in part, a steel that is preselected. The permanent magnetgenerator is structured to: (i) meet a hot generator, high current,transient loaded, minimum voltage point requirement by maintainingrelative apparent permeability of the steel below a first limit, and(ii) meet a cold generator, no load current, working point maximumvoltage limit requirement.

A method for constructing a generator for connecting to a load definesfurther embodiments of the invention. The method includes (i) providinga stator comprising at least a plurality of stator coils and a statorcore with a plurality of stator slots, wherein the stator core comprisesa stator lamination stack made of steel, (ii) providing a rotorcomprising a rotor core with a rotor lamination stack made of steel anda plurality of permanent magnets for establishing a rotating magneticfield within the generator. The generator is structured to: (i) meet ahot generator, high current, transient loaded, minimum voltage pointrequirement and by maintaining relative apparent permeability of thesteel below a first limit, and (ii) meet a cold generator, no loadcurrent, working point maximum voltage limit requirement.

In specific embodiments of the method, the generator is structured tomeet the cold generator, no load current working point, maximum voltagelimit requirement by maintaining the relative apparent permeabilityabove a second limit. In a specific embodiment, the second limit is 10.

In other specific embodiments the method further includes (i) selectinga grade type of the steel, with a saturation flux density for the statorlamination stack of the stator to meet voltage requirements of the load,(ii) selecting a number of the plurality of stator slots to meet thevoltage requirements of the load, (iii) selecting an outside diameter ofstator lamination to meet the voltage requirements of the load, (iv)selecting a length of the stator lamination stack to meet the voltagerequirements of the load, (v) selecting a number of the plurality ofpermanent magnets for placing within the rotor to meet a frequencyrequirement of the load, (vii) selecting magnetic polarization for theplurality of permanent magnets to provide the rotating magnetic fieldwithin the generator to meet a voltage requirement of the load, (viii)selecting number of series turns per phase, (ix) selecting size of thegenerator, and (x) selecting an inductance of the generator.Additionally, one or more of (i) the saturation flux density of thegrade type of the steel, (ii) the number of the plurality of slots,(iii) the outside diameter of the stator lamination, (iv) the length ofthe stator lamination stack, (v) the magnetic polarization of thepermanent magnets, (vi) temperature of the generator, (vii) currentdrawn by the load, (viii) the size of the generator, (ix) the number ofseries turns per phase of the generator, and (x) the inductance of thegenerator, regulate the output of the generator.

In specific embodiments of the method, the number of the plurality ofslots is 36. While in other specific embodiments, the number of thepermanent magnets is 4. In one specific embodiment of the method, theoutside diameter of the stator is between 253 mm and 342 mm and/or thelength of the stator lamination stack is between 145 mm and 196 mm. Inyet another specific embodiment of the method, the first limit is 500and the second limit is 10. In a further embodiment of the method, theload is an induction motor that drives a refrigeration unit to maintaina temperature at or below 6 degree Celsius.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other advantages and features of the invention, andthe manner in which the same are accomplished, will become more readilyapparent upon consideration of the following detail description of theinvention taken in conjunction with the accompanying drawings, whichillustrate preferred and exemplary embodiments and which are notnecessarily drawn to scale, wherein:

FIG. 1 illustrates a block diagram presenting a generator that isstructured to connect to a predefined load, according to embodiments ofthe present invention.

FIG. 2 illustrates a B-H curve associated with steel to be used in thegenerator to meet requirements of the load, according to embodiments ofthe present invention.

FIGS. 3A-3B illustrate B-H and relative apparent permeability curves ofdifferent grades of steel, according to embodiments of the presentinvention.

FIG. 4 illustrates a cross sectional view of the generator, according toa embodiments of the present invention.

FIG. 5A illustrates a rotor of the generator, according to a embodimentsof the present invention.

FIG. 5B illustrates the rotor of the generator connected to a shaft,according to a embodiments of the present invention.

FIG. 6A illustrates a stator of the generator, according to embodimentsof the present invention.

FIG. 6B illustrates a stator core of the generator, according toembodiments of the present invention.

FIG. 7 illustrates a configuration of the generator of FIG. 1, accordingto embodiments of the present invention.

FIG. 8 illustrates a configuration of the generator of FIG. 1, accordingto embodiments of the present invention.

FIG. 9 illustrates a process flow of constructing the generator of FIG.1, according to embodiments of the present invention.

DETAILED DESCRIPTION OF AN EMBODIMENT OF THE INVENTION

The present invention now will be described more fully hereinafter withreference to the accompanying drawings, in which some, but not allembodiments of the invention are shown. This invention may be embodiedin many different forms and should not be construed as limited to theembodiments set forth herein; rather, these embodiments are provided sothat this disclosure will be thorough and complete, and will fullyconvey the scope of the invention to those skilled in the art. Likenumbers refer to like elements throughout.

Generators have many applications and are designed to meet requirementsof different types of load as explained above. Loads connected togenerators may be linear loads and/or non-linear loads. Examples oflinear loads may include, but are not limited to, heaters, motors,transformers, or the like. Examples of non-linear loads may include, butare not limited to computer, Uninterruptable Power Supplies (UPSs),electronic equipment, variable frequency drives, or the like. Each ofthese loads may have different requirements and therefore generatorsused for each of these applications differ in configuration, size,and/or operation.

One application addressed in the present invention is to construct agenerator that ultimately drives a stand-alone refrigeration unit or arefrigeration unit located in a truck, tractor, trailer, semi-trailer,or the like used to transport medical supplies, pharmaceutical products(e.g., medicines), perishable products (e.g., meat, dairy, poultry,seafood, or the like), chemical products, or the like. Such anapplication requires a generator that meets specific voltage, size,efficiency, and/or cost requirements in order to maintain a temperatureat or below 6 degrees Celsius within the truck, trailer, semi-trailer,or the like. In particular, a generator used in such an applicationrequires (i) a minimum voltage while starting an inductive load (e.g.,induction motor) at or above ambient temperature, and (ii) an outputvoltage that does not exceed an upper voltage limit while being drivenat full speed without any load current at or below ambient temperatures,while maintaining high efficiency under a specified full load runningcondition and keeping the overall cost and size of the generator low.

Conventional generators existing in such applications are designed usingthicker and stronger magnets and/or high number of slots, therebydriving up the size and cost of the generators. Bulky generators thatcost more are usually not desirable. As such, there exists a need for agenerator that meets specific requirements of the predefined load (i.e.,an induction motor that drives the refrigeration unit). The presentinvention discloses a novel generator that is structured to meet thespecific voltage requirements while keeping the size and cost of thegenerator low and efficiency of the generator high.

FIG. 1 illustrates a block diagram 100 of a generator of the presentinvention that is designed and structured to meet requirements of apredefined load. As shown, generator 120 of the present invention isconnected to a predefined load, where the predefined load is aninduction motor 130 which is used to drive a refrigeration unit 140. Thegenerator 120 is driven by an engine 110 that controls the speed of theengine generator set to provide a frequency required by the predefinedload. In one preferred embodiment of the present invention, the engine110 is a diesel engine. The generator 120 is designed and structured tomeet the requirements of a predefined load by relying at least in parton magnetic characteristics of steel that is used in the generatorwithout having to use stronger and/or thicker magnets that are costprohibitive.

FIG. 2 illustrates a B-H curve associated with steel to be used in thegenerator to meet requirements of the load, according to embodiments ofthe present invention. In some embodiments, to maintain the outputvoltage of the generator above a transient required voltage whilestarting the predefined load when at or above ambient temperature and tomaintain the output voltage of the generator below an voltage upperlimit when running with no load current at or below ambienttemperatures, a grade type of steel is selected to construct thegenerator 120 such that the steel has (i) an apparent relativepermeability below 500 for point 210 of FIG. 2 and/or (ii) an apparentrelative permeability above 10 for point 220 of FIG. 2. Relativeapparent permeability is defined as the ratio of flux density (B) to theapplied magnetic field strength (H). As shown, the region of delta B(ΔB) is defined as the difference between a minimum flux density(B_(min)) (i.e., point 210 of FIG. 2) of the steel required to meet thetransient voltage requirement while starting the predefined load when ator above ambient temperature and a maximum flux density Point (B_(max))(i.e., point 220 of FIG. 2) of the steel required to stay within themaximum output voltage of the generator when running with no loadcurrent at or below ambient temperatures.

As shown in FIG. 2, a knee region of the B-H curve is a portion of thecurve where the relative apparent permeability starts to rapidly changeout of saturation with decreasing flux density (B). In the region of theB-H curve that is above the knee region, the steel used in the generatoris in a high degree of saturation. If the flux density (B) of the steelis at point 220 (B_(max)) when the generator is running with no load ator below ambient temperatures, then while starting the predefined load,current is drawn by the predefined load, thereby potentially causing thepoint 210 (B_(min)) to drop below the knee region of the B-H curve andthe generated voltage may drop below the limit required to start theinduction motor, which is not desirable. Therefore, it is important forB_(min) to stay as high on the B-H curve as possible while still havingthe B_(max) not to cause a voltage to exceed the maximum voltage limitof the generator. In other words, the region of delta B (ΔB) should beminimized, which is possible when the B_(min) is high on the knee regionof the B-H curve, that is below a relative apparent permeability limit.The highly saturated condition of the steel minimizes the change in fluxdensity (B) between the hot generator, transient loaded condition andthe cold generator no load current condition, thereby keeping thegenerator within the specified voltage limits. In some embodiments, agrade type of steel is selected such that the relative apparentpermeability of the steel is below 500 and above 10 to meet the voltagerequirements of the predefined load.

FIG. 3A illustrates B-H curves of different grades of steel, accordingto an embodiment of the present invention. As shown, the curve 310illustrates the B-H curve for M470-50A grade electrical steel and thecurve 320 illustrates the B-H curve for M210-35A grade electrical steel.As shown, the B_(max) (i.e., point 314 associated with curve 310 andpoint 324 associated with curve 320) and B_(min) (i.e., point 312associated with curve 310 and point 322 associated with curve 320) valuefor both the curves 310 and 320 is the same. Therefore, both gradesteels have the same delta B (ΔB) such that both grade steels will meetthe voltage requirements of the predefined load. However, the magneticfield strength (H) required to achieve the B_(min) and B_(max) values inM210-35A grade electrical steel is higher than the M470-50A gradeelectrical steel. If the M210-35A grade electrical steel is selected fordesigning and constructing the generator, a higher grade magnet or alonger magnet in the direction of magnetization with higher fieldstrength is required, thereby driving up the cost of the generator.

FIG. 3B illustrates relative apparent permeability curves of differentgrades of steel, according to an embodiment of the present invention. Asshown, curve 330 is the relative apparent permeability curve forM470-50A grade electrical steel, curve 340 is the relative apparentpermeability curve for M1000-65A grade electrical steel, and curve 350is the relative apparent permeability curve for M210-35A gradeelectrical steel. For a given magnetic polarization, the relativeapparent permeability curves of different grades of steel shown in FIG.3B meet the flux density requirements of the predefined load describedin FIG. 2. As mentioned above, any of the different grades of steelshown in FIG. 3B may be used in the generator 120. Typically, highergrade electrical steels cost more and have lower losses when comparedwith lower grade electrical steels that cost less. The M210-35A gradeelectrical steel is a higher grade steel when compared with the M470-50Agrade electrical steel and the M1000-65A grade electrical steel. Asexplained in FIG. 3A, the amount of field strength (H) required for theM210-35A grade electrical steel is higher than the M470-50A gradeelectrical steel to achieve the required B_(max) and B_(min) values.Although a higher grade steel is desirable because of lower losses, thecost of the higher grade steel and the additional magnet volume requiredby the higher grade steel can be prohibitive. The overall cost of thegenerator is balanced based on selection criteria explained in FIGS. 3Aand 3B. In one preferred embodiment, M470-50A grade electrical steel isused in the generator 120 of the present invention to meet the costrequirements and the voltage requirements of the predefined load.

FIG. 4 illustrates a cross sectional view of the generator 120,according to an embodiment of the present invention. In someembodiments, the generator 120 is a three-phase generator. The generator120 that is designed and constructed to meet the predefined loadrequirements, comprises at least a rotor assembly 500 and a stator 600.In some embodiments of the present invention, the generator 120 is apermanent magnet generator, where the generator 120 comprise one or morepermanent magnets. The generator 120 may be an ‘n’ pole generator, where‘n’ presents the number of poles. The number of poles ‘n’ are selectedbased on the frequency requirements of the predefined load and/or thespeed of the rotor 500.

In a preferred embodiment of the present invention, the permanent magnetgenerator 120 is a four-pole generator comprising four sets of permanentmagnets 510 a, 510 b, 510 c, and 510 d that are placed inside the rotorassembly 500. In some embodiments, the sets of permanent magnets 510 a,510 b, 510 c, and 510 d may be rare earth magnets. The sets of permanentmagnets 510 a, 510 b, 510 c, and 510 d may be pre-magnetized magnetsthat create persistent magnetic field with a predefined magnetic fieldintensity within the generator. The sets of permanent magnets 510 a, 510b, 510 c, and 510 d are selected in conjunction with the grade type ofsteel selected for the generator.

FIG. 5A illustrates the rotor assembly 500 of the generator 120,according to an embodiment of the present invention. In someembodiments, the rotor assembly 500 comprises one or more laminatedsheets made from the preselected steel and sets of permanent magnets.FIG. 5B illustrates the rotor assembly 500 of the generator 120connected to a shaft, according to an embodiment of the presentinvention. The shaft 510 of the generator is connected to the engine 110of FIG. 1 to drive the generator engine set to provide a frequencyrequired by the predefined load. The permanent magnets 510 a, 510 b, 510c, and 510 d placed in the rotor produce a rotating magnetic fieldwithin the generator 120 when connected to the shaft 510, where therotating magnetic field cuts the coils present in the stator 600.

FIG. 6A illustrates a stator 600 of the generator, according to anembodiment of the present invention. The stator 600 comprises a statorcore 610 as illustrated in FIG. 6B, according to an embodiment of thepresent invention. The stator 600 comprises one or more stator coils 630placed in one or more stator slots 620 of the stator core 610. In someembodiments, an optimum number of the one or more stator slots selectedfor the generator are 36 based on the generator size and inductancerequirements associated with the predefined load. In some embodiments,the number of the one or more stator slots selected for the generator120 may be lower or higher than 36. However, increase in the number ofthe one or more stator slots increases the losses of the generator for agiven size of the generator. The stator core 630 comprises one or morelaminated sheets made from the preselected steel. In some embodiments,the outside diameter of the stator is between 253 mm and 342 mm. In apreferred embodiment, the optimum outside diameter of the stator is297.23 mm. In some embodiments, the length of the stator laminationstack is between 145 mm and 196 mm. In a preferred embodiment, theoptimum outside diameter of the stator lamination stack is 170.66 mm.The relative apparent permeability induced in the preselected steel ofthe generator is dependent on the outside diameter of the stator 500,the length of the stator 500, the magnetic field produced by thepermanent magnets 510 a, 510 b, 510 c, and 510 d and series turns perphase of the generator.

The generator 120 does not comprise any control or regulating mechanismto control the output of the generator, which reduces the overall sizeand cost of the generator 120. Instead, the generator 120 is designedsuch that the output voltage produced by the generator 120 meets thevoltage requirements of the predefined load based on the magnetic fieldproduced by the permanent magnets 510 a, 510 b, 510 c, and 510 d,magnetic characteristics of the preselected steel, the internaltemperature of the generator which is in turn dependent on the ambienttemperature, demagnetizing field resulting from the current drawn by thepredefined load, size of the generator, number of series turns per phasein the generator, and inductance of the generator.

The magnetic field produced by the preselected permanent magnets 510 a,510 b, 510 c, and 510 d of a predefined field strength causes thepreselected steel to reach a level of saturation beyond the knee of theB-H curve. Once the level of saturation beyond the knee of the B-H curveis reached, even a significant change in the magnetic field strengthdoes not cause a lot of change in the flux density of the preselectedsteel, thereby causing a very small change in the output voltage of thegenerator 120. After the preselected steel reaches the saturation regionthat is above the knee of the B-H curve, the demagnetizing field fromthe current drawn by the predefined load and the internal temperature ofthe generator 120 control the output voltage of the generator 120 tomeet the voltage requirements of producing an output voltage that isabove a transient required voltage to start the predefined load when ator above ambient temperature and to maintain the output voltage below avoltage upper limit when running with no load current at or belowambient temperatures.

Additionally, the size of the generator and the type of permanentmagnets are interdependent on each other which have an effect on theoutput voltage of the generator. If the size of the generator selectedis large, the amount of magnetic flux passing through the steel (i.e.,flux density (B)) of the generator is greater, thereby not requiring amagnet with higher field strength (H). In some embodiments, the size ofthe generator is based on the application associated with the generator.For example, the size of the generator to be used in a truck may varyfrom that of a generator designed for a small trailer. In addition tothis interdependency, inductance of the generator is interdependent onthe number of series turns per phase of the generator. If the number ofseries turns per phase used in the generator is higher, the inductanceof the generator is high and vice versa. The number of series turns perphase are selected such that the inductance of the generator is not toohigh, since higher inductance lowers the total magnetic flux within themagnetic circuit of the generator because of the demagnetizing fieldfrom the current drawn by the predefined load.

Selection of the grade type of the steel, a number of the plurality ofstator slots, outside diameter of stator lamination to meet the voltagerequirements of the load, length of the stator lamination stack to meetthe voltage requirements of the load, a number of the plurality ofpermanent magnets for placing within the rotor, magnetic polarizationassociated with the plurality of permanent magnets, size of thegenerator, number of series turns per phase of the generator, andinductance of the generator have an effect on the output voltage of thegenerator. One or more of these selections are based on the requirements(e.g., voltage requirements, size requirements, cost requirements,efficiency requirements, power requirements, or the like) of thepredefined load. As explained above, one or more of these selections maybe interdependent on each other which drive the overall cost, size, andoutput of the generator.

Although the present invention discloses a generator that serves arefrigeration unit in a truck, tractor, trailer, semi-trailer, or thelike, it should be understood that the generator described herein may beapplicable for any loads that have similar voltage requirements atspecific temperatures, cost requirements, size requirements, and/orefficiency requirements.

FIG. 7 illustrates a configuration of the generator of FIG. 1, accordingto an embodiment of the present invention. In a first preferredembodiment of the present invention, the generator 120 comprises astator 600 comprising at least a stator core 610 with a plurality ofstator slots and a plurality of stator coils. The stator core 610comprises stator lamination stack that is made of steel. In the firstpreferred embodiment of the present invention, the generator 120comprises a rotor further comprising (i) a rotor core, where the rotorcore comprises a rotor lamination stack made of the steel, and (ii) aplurality of permanent magnets 510 for establishing a rotating magneticfield within the generator 120. The generator 120 according to the firstpreferred embodiment of the present invention is structured to meet ahot generator, high current, transient loaded minimum voltage workingpoint requirement by maintaining relative apparent permeability of thesteel below a first limit and to meet a cold generator, no load currentworking point, maximum voltage limit requirement.

FIG. 8 illustrates a configuration of the generator of FIG. 1, accordingto an embodiment of the present invention. In a second preferredembodiment of the present invention, the generator 120 comprises agenerator magnetic circuit 800, where the generator magnetic circuitcomprises at least in part a preselected steel. The generator 120according to the second preferred embodiment of the present invention isstructured to meet a hot generator, high current, transient loadedminimum voltage working point requirement by maintaining relativeapparent permeability of the steel below a first limit and to meet acold generator, no load current working point, maximum voltage limitrequirement.

FIG. 9 illustrates a process flow 900 of constructing the generator ofFIG. 1, according to an embodiment of the present invention. As shown inblock 910 of the process flow 900, the method of constructing thegenerator comprises providing a stator comprising at least a stator corewith a plurality of stator slots and a plurality of stator coils,wherein the stator core comprises a stator lamination stack made ofsteel. As shown in block 920 of the process flow 900, the method ofconstructing the generator comprises providing a rotor comprising (i) arotor core, where the rotor core comprises a rotor lamination stack madeof the steel, and (ii) a plurality of permanent magnets for establishinga rotating magnetic field within the generator. The generatorconstructed based on the process flow 900 meets a hot generator, highcurrent, transient loaded minimum voltage working point requirement bymaintaining relative apparent permeability of the steel below a firstlimit and meets a cold generator, no load current working point, maximumvoltage limit requirement.

Many modifications and other embodiments of the inventions set forthherein will come to mind to one skilled in the art to which theseinventions pertain having the benefit of the teachings presented in theforegoing descriptions and the associated drawings. Therefore, it is tobe understood that the inventions are not to be limited to the specificembodiments disclosed and that modifications and other embodiments areintended to be included within the scope of the appended claims.Although specific terms are employed herein, they are used in a genericand descriptive sense only and not for purposes of limitation. Inaddition, where possible, any terms expressed in the singular formherein are meant to also include the plural form and/or vice versa. Asused herein, “at least one” shall mean “one or more” and these phrasesare intended to be interchangeable. Accordingly, the terms “a” and/or“an” shall mean “at least one” or “one or more,” even though the phrase“one or more” or “at least one” is also used herein.

What is claimed is:
 1. A generator for connecting to a load, thegenerator comprising: a stator comprising at least a plurality of statorcoils and a stator core with a plurality of stator slots, wherein thestator core comprises a stator lamination stack made of steel; a rotorcomprising: a rotor core comprising a rotor lamination stack made of thesteel; and a plurality of permanent magnets for establishing a rotatingmagnetic field within the generator; wherein the generator is structuredto: meet a hot generator, high current, transient loaded minimum voltageworking point requirement by maintaining relative apparent permeabilityof the steel below a first limit; and meet a cold generator, no loadcurrent working point, maximum voltage limit requirement.
 2. Thegenerator of claim 1, wherein the generator is structured to meet thecold generator, no load current working point, maximum voltage limitrequirement by maintaining the relative apparent permeability above asecond limit.
 3. The generator of claim 2, wherein the first limit is500 and the second limit is
 10. 4. The generator of claim 1, wherein theoutput voltage of the generator is dependent on, at least in part, therelative apparent permeability of the steel, wherein the relativeapparent permeability of the steel at the hot generator, high current,transient loaded minimum voltage working point requirement and the coldgenerator, no load current working point, maximum voltage point limitrequirement is dependent on at least one selected from the groupcomprising (i) a grade type of the steel (ii) magnetic polarization ofthe plurality of magnets, (iii) temperature of the generator, (iv)current drawn by the load, (v) size of the generator, (vi) number ofseries turns of the generator and (vi) inductance of the generator. 5.The generator of claim 1, wherein the plurality of stator slots is 36and the plurality of permanent magnets are
 4. 6. The generator of claim1, wherein an outside diameter of the stator is between 253 mm and 342mm.
 7. The generator of claim 1, wherein a length of the statorlamination stack of the stator is between 145 mm and 196 mm.
 8. Thegenerator of claim 1, wherein the generator is connected to an inductionmotor load that drives a refrigeration unit to maintain a temperature ator below 6 degree Celsius.
 9. A generator for connecting to a predefinedload, the generator comprising: a generator magnetic circuit, whereinthe generator magnetic circuit comprises at least in part a steel thatis preselected; wherein the generator is structured to: meet a hotgenerator, high current, transient loaded, minimum voltage pointrequirement by maintaining relative apparent permeability of the steelbelow a first limit; and meet a cold generator, no load current, workingpoint maximum voltage limit requirement.
 10. The generator of claim 9,wherein the generator magnetic circuit further comprises a statorcomprising at least a plurality of stator coils and a stator core with aplurality of stator slots, wherein the stator core comprises a statorlamination stack made of steel.
 11. The generator of claim 10, whereinoutside diameter of the stator is between 253 mm and 342 mm.
 12. Thegenerator of claim 10, wherein length of stator lamination stack isbetween 145 mm and 196 mm.
 13. The generator of claim 10, wherein theplurality of stator slots is
 36. 14. The generator of claim 9, whereinthe generator magnetic circuit further comprises a rotor comprising (i)a rotor core comprising a rotor lamination stack made of the steel and(ii) a plurality of permanent magnets for establishing a rotatingmagnetic field within the generator, where a core of the rotor is madeof the steel.
 15. The generator of claim 14, wherein the output voltageof the generator is dependent on, at least in part, the relativeapparent permeability of the steel, wherein the relative apparentpermeability of the steel is dependent at least one selected from thegroup comprising (i) a grade type of the steel, (ii) magneticpolarization of the plurality of magnets, (iii) temperature of thegenerator, (iv) current drawn by the load, (v) size of the generator,(vi) number of series turns of the generator and (vi) inductance of thegenerator.
 16. The generator of claim 14, wherein the plurality ofpermanent magnets is
 4. 17. The generator of claim 9, wherein the firstlimit is
 500. 18. A permanent magnet generator for a preselected load,wherein the permanent magnet generator comprises a generator magneticcircuit, wherein the generator magnetic circuit comprises, at least inpart, a steel that is preselected; wherein the permanent magnetgenerator is structured to: meet a hot generator, high current,transient loaded, minimum voltage point requirement by maintainingrelative apparent permeability of the steel below a first limit; andmeet a cold generator, no load current, working point maximum voltagelimit requirement.
 19. A method of constructing a generator forconnecting to a load, wherein the method comprises: providing a statorcomprising at least a plurality of stator coils and a stator core with aplurality of stator slots, wherein the stator core comprises a statorlamination stack made of steel; providing a rotor comprising: a rotorcore comprising a rotor lamination stack made of the steel; and aplurality of permanent magnets for establishing a rotating magneticfield within the generator; wherein the generator is structured to: meeta hot generator, high current, transient loaded, minimum voltage pointrequirement and by maintaining relative apparent permeability of thesteel below a first limit; and meet a cold generator, no load current,working point maximum voltage limit requirement.
 20. The method of claim19, further comprising: (i) wherein the step of providing a statorcomprises: selecting a grade type of the steel, with a saturation fluxdensity for the stator lamination stack of the stator to meet voltagerequirements of the load; selecting a number of the plurality of statorslots to meet the voltage requirements of the load; selecting an outsidediameter of stator lamination to meet the voltage requirements of theload; and selecting a length of the stator lamination stack to meet thevoltage requirements of the load; (ii) wherein the step of providing arotor comprises: selecting a number of the plurality of permanentmagnets for placing within the rotor to meet a frequency requirement ofthe load; and selecting magnetic polarization for the plurality ofpermanent magnets to provide the rotating magnetic field within thegenerator to meet a voltage requirement of the load; and selecting sizeof the generator; (iii) wherein the method further comprises: selectingnumber of series turns per phase of the generator; and selecting aninductance of the generator; and (iv) wherein the output of thegenerator is regulated by at least one selected from the groupcomprising (a) the saturation flux density of the grade type of thesteel, (b) the number of the plurality of slots, (c) the outsidediameter of the stator lamination, (d) the length of the statorlamination stack, (e) the magnetic polarization of the permanentmagnets, (f) temperature of the generator, (g) current drawn by theload, (h) the size of the generator, (i) the number of series turns perphase of the generator, and (j) the inductance of the generator.
 21. Themethod of claim 20, wherein the number of the plurality of slots is 36.22. The method of claim 20, wherein the number of the permanent magnetsis
 4. 23. The method of claim 20, wherein the outside diameter of thestator is between 253 mm and 342 mm.
 24. The method of claim 20, whereinthe length of the stator lamination stack is between 145 mm and 196 mm.25. The method of claim 20, wherein the first limit is
 500. 26. Themethod of claim 19, wherein the load is an induction motor that drives arefrigeration unit to maintain a temperature at or below 6 degreeCelsius.
 27. The method of claim 19, wherein the generator is structuredto meet the cold generator, no load current working point, maximumvoltage limit requirement by maintaining the relative apparentpermeability above a second limit.
 28. The method of claim 27, whereinthe second limit is 10.